Actually it doesn't relate to printed material. It could be everything like a speech or something or a story..
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TarikSep 1 '11 at 19:28

Lets assume "Some one is giving a speech about something but in the middle of his speech he just decided to give such info not relevant to the topic and then quickly got back to the topic" but he did it on purpose and this is something not necessary and also detail info about the topic.
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TarikSep 1 '11 at 19:38